Part 121 of the Federal Aviation Regulations (FARs, 121.383c) contains a provision for mandatory retirement of airline pilots at age 60. The "Age-60 Rule" was established in 1959 with "... the objective of reducing aircraft accidents attributable to the effects of pilot aging." The logic behind this decision was that ... progressive deterioration of physiological and psychological functions regularly accompanied increasing age" (From historical review by Kay et al., 1993, 1-1). Despite this rationale, there has been little data collected to examine actual performance of aviators in this age group to objectively evaluate this rule. For several years our laboratory has studied the effects of age and drugs on aircraft pilot performance using flight simulator measures and computerized cognitive testing. Moreover, we have extensive experience in conducting longitudinal studies. In this context, we propose a longitudinal study to evaluate objectively age-related changes in flight performance of aviators 50 to 70 years of age. Furthermore, in our extensive work with normal older adults we have been impressed by the wide variability of performance in older populations, including aviators. We believe that some cognitive ability measures may predict aviation performance better than age alone. Therefore, in our proposed work, we will include carefully selected cognitive measures to explain variability in aviation performance among older pilots. In the proposed work we will address the following key issues: 1) Overall Effects Of Age on Aviation Performance In Pilots Aged 50 to 70. Using an accelerated longitudinal study design, we plan to determine if there are significant age-related changes in performance among aviators 50 to 70 years old. We will follow 100 pilots over a three-year period and use regression analyses to evaluate the effects of chronological age on performance over time. (2) Overall Effects of Processing Speed on Aviation Performance. In the past we and others have found, on a cross-sectional basis, that performance on measures of speed of processing and working memory is correlated with performance on aviation-related tasks. We plan to test the hypothesis that longitudinal simulator performance can be predicted by measures of cognitive processing speed.